I recently tried to install the Hope gtk3 theme, to change the looks of the default Gnome 3. It's working properly, except for one thing: the top panel's theme is not changing. So, how exactly do you change it?
Backup default theme on
Paste your new gnome shell theme folder into
(Normally theme creator will rename that folder as gnome-shell)
Rename new gnome-shell folder to theme.
Press Alt+F2+r and hit Enter button.